Our invention relates broadly to apparatus having one or two transducer heads for data transfer with one or both sides of a record medium such as a flexible magnetic disk, or a floppy disk according to common parlance, that may be housed in a protective envelope to make up a disk cartridge. More specifically, our invention pertains to a flexure seat for use in such apparatus for resiliently supporting the transducer head or either or both of the two transducer heads.
Flexible magnetic disks may be described as being either single or double sided depending upon one or both sides of the disk are used for data transfer. Double sided disks are, of course, preferable from the standpoint of greater capacity. Devices having a pair of transducer heads for data transfer with such double sided magnetic disks are described and claimed in Castrodale et al. U.S. Pat. No. 4,089,029 and Tandon et al. U.S. Pat. No. 4,151,573. In the Castrodale et al. apparatus the transducer heads are both gimbal supported on a carriage composed of two parts of symmetrical design with respect to the plane of the magnetic disk intervening therebetween. So supported, the transducer heads can closely follow the unavoidable undulations or perturbations of the disk and cause little disk wear. However, when the disk plane considerably deviates from its normal plane, the gimbaled transducer heads are very easy to go off the track. We also object to the gimbal supporting of transducer heads as they are susceptible to rolling and pitching during data transfer, making difficult the high density recording of data on the magnetic disk.
With a view to minimal mistracking, Tandon et al. suggests the rigid mounting of one transducer head on a carriage movable radially of the magnetic disk, and the gimbaling of the other transducer head on a load arm pivoted on the carriage. Although mistracking is certainly reduced by this known arrangement, we nevertheless object to it, particularly to the fixed mounting of one transducer head. The position of the magnetic disk with respect to the fixed head is subject to change with the dimensional errors of the disk drive mechanism or of the disk cartridge itself. Therefore, as both heads are loaded against the disk, the latter must be elastically deformed into data transfer contact with the fixed head by the application of a high loading pressure. The high loading pressure is a cause of rapid disk wear. As an additional drawback the gimbaled head gives rise to problems similar to those set forth previously in conjunction with the gimbaling of both heads.
It will have been seen from the foregoing discussion of the prior art that the transducer heads should be resiliently supported for displacement only in a direction perpendicular to the plane of the magnetic disk. We designed an experimental flexure seat which we thought was capable of so supporting a transducer head. In the form of a unitary piece of resilient sheet metal material, the experimental flexure seat comprised a central portion of circular shape, an annular peripheral portion surrounding the central portion with a spacing therefrom, and three or more deflective bridge portions interposed at constant angular spacings from each other between the central and peripheral portions for interconnecting them. The central portion was intended to have a transducer head fixedly mounted thereon, and the peripheral portion to be secured to the carriage or the load arm. Each bridge portion took the form of a relatively slender strip of arcuate shape extending through an angle of, say, approximately 60 degrees about the axis of the central portion, joined at its opposite extremities to the central and peripheral portions. Extending along the periphery of the central portion, the bridge portions were highly deflective to permit large displacement of the central portion, and therefore of the transducer head thereon, in a direction normal to the principal plane of the flexure seat.
However, we found a fatal defect in this experimental flexure seat. Being joined at its opposite extremities to the central and peripheral portions, each bridging strip deflected about its joint to the peripheral portion upon displacement of the central portion in the direction normal to the principal seat plane, thereby giving rise to concurrent rotary displacement of the central portion. Such rotary displacement of the central portion, and hence of the transducer head thereon, is objectionable as it results in mistracking.